Islamic State fighters closed in Tuesday on the Iraqi town of Amriyat al-Fallujah, one of the last still controlled by the government in the troubled western province of Anbar, its police chief said.
"IS has come from three directions; we are almost besieged," Aref al-Janabi told AFP by telephone.
"So far we are still standing," he said. "We have some support from tribal fighters, but if Amriyat falls, the battle will move to the gates of Baghdad and Karbala."
Amriyat al-Fallujah lies around 35 kilometres (20 miles) west of Baghdad's limits, and IS fighters would have to capture a significant stretch of government-controlled land before reaching the capital.
The town also lies between the IS bastion of Fallujah, further up the Euphrates River, and the contested area of Jurf al-Sakhr, which commands access to the holy Shiite city of Karbala.
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Government forces have suffered a string of bruising military setbacks in Anbar in recent weeks, prompting some officials to warn that the entire province could fall within days.
Soldiers pulled out of a base near the city of Heet and regrouped in a large desert airbase, while government forces struggled to hold their ground in the provincial capital Ramadi.
Some officials in Anbar have argued that anything short of an intervention by US ground forces would lead to Anbar falling into jihadist hands.
On Tuesday, a Sunni tribal leader based in Kurdistan, Sheikh Ali Hatem al-Suleiman, even called for troops from the Arab nations involved in the US-led anti-jihadist coalition to deploy in Iraq.
But the head of Iraq's Shiite-dominated government, Prime Minister Haidar al-Abadi, has ruled out any foreign ground intervention.
While IS fighters have not moved closer to Baghdad in recent weeks, the group has claimed responsibility for a string of deadly suicide attacks in the capital.
A suicide car bomb blast claimed by IS on Tuesday killed a member of parliament who was also a prominent leader in the Iran-backed Badr Shiite militia.